Application of high intensity focused ultrasound to the displacement of drilling mud

ABSTRACT

A method for disrupting an obstruction from a wellbore includes determining a location of an obstruction within a wellbore. An ultrasound transducer is deployed down an interior of a casing in the wellbore. Ultrasound energy is focused, using the ultrasound transducer, to the determined location of the obstruction and the obstruction is disrupted using the focused ultrasound energy.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based on provisional application Ser. No. 61/660,230, filed Jun. 15, 2012, the entire contents of which are herein incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to deep water drilling and, more specifically, to the application of high intensity focused ultrasound (HIFU) to the displacement of drilling mud in deep water drilling.

DISCUSSION OF THE RELATED ART

Deep water drilling is the practice of harvesting hydrocarbons such as oil and gas by conducting drilling operations off of a platform, rig or ship that is located out at sea. In performing deep water drilling, a drill may be lowered to the sea floor and the sea floor may be drilled to create a borehole, which may also be called a wellbore. As the wellbore is drilled, drilling mud may be deployed to fill the wellbore. The mud may be used to maintain the structural integrity of the wellbore as it is being drilled, for example, to prevent the sidewalls of the wellbore from collapsing.

After drilling is complete, or as drilling is being performed, a casing may be deployed into the wellbore. The casing may be a pipe-like structure that may have, for example, multiple sections, which extend downward with decreasing radii in a manner similar to that of an extending car antenna. The drilling mud may be removed from the annular space between the casing and the borehole and cement may be deployed therein. The cement, upon hardening, may serve to maintain the borehole, stabilize the casing, and help to prevent communication of substances up the wellbore between the interior of the casing and the borehole.

However, it is possible that not all of the mud can be effectively removed from the annular region between the casing and the borehole. The drilling mud may thereby harden and cake upon the walls of the casing. In this event, the cement may not properly adhere to mud cake disposed on the inner surface of the borehole and/or the outer surface of the casing. Moreover, by blocking the deployment of the cement, the mud cake may create channels in the cement, which may lead to reduced effectiveness, potential leaks and even lead to the possibility of potentially catastrophic blowouts.

SUMMARY

A method for disrupting an obstruction from a wellbore includes determining a location of an obstruction within a wellbore. An ultrasound transducer is deployed down an interior of a casing in the wellbore. Ultrasound energy is focused, using the ultrasound transducer, to the determined location of the obstruction. The obstruction is disrupted using the focused ultrasound energy.

Determining the location of the obstruction within the wellbore may include acquiring a sequence of ultrasound images, using the ultrasound transducer, of an area exterior to the casing, as the ultrasound transducer is deployed down the interior of the casing, analyzing the acquired images to detect the obstruction, and determining the location of the obstruction from the acquired images.

The ultrasound transducer may include a plurality of ultrasound transducers.

The plurality of ultrasound transducers may be arranged in a circle substantially conforming to a radius of the casing. The plurality of ultrasound transducers may be arranged along a lengthwise direction of the casing or in two-dimensions over a surface in the casing. The plurality of ultrasound transducers may be arranged as a set of annular rings.

Disrupting the obstruction may include breaking the obstruction down into a plurality of smaller sections or particles. Disrupting the obstruction may include increasing the movability of the obstruction. Disrupting the obstruction may include liquefying the obstruction via a pulsed insonication. Disrupting the obstruction may include performing erosive cavitation.

Prior to deploying the ultrasound transducer array down the interior of the casing, the wellbore may be drilled, drilling mud may be pumped therein, the casing may be lowered into the wellbore, and an attempt to clear the drilling mud from an annular region between the exterior of the casing and interior of the wellbore may be made.

The ultrasound transducer may include one or more ultrasound imaging devices for determining the location of the obstruction as the ultrasound transducer is deployed.

The one or more ultrasound imaging devices may determine the location of the obstruction by imaging over a 360° field.

The obstruction may include drilling mud remaining in an annular region between the casing and the wellbore. The obstruction may include a channel or other irregularity within cement in an annular region between the casing and the wellbore.

Focusing the ultrasound energy may include performing high intensity focused ultrasound (HIFU).

Disrupting the obstruction using the focused ultrasound energy may include performing a flushing operation to clear the obstruction after it has been at least partially broken down by the focused ultrasound energy.

A method for establishing a well for deep water drilling includes drilling a wellbore below the sea floor. A drilling mud is pumped into the wellbore. A casing is deployed into the wellbore. The drilling mud is partially removed from an annular region between the casing and the wellbore. A location of an area of remaining drilling mud in the annular region is determined. An ultrasound transducer is deployed down an interior of the casing. Ultrasound energy is focused, using the ultrasound transducer array, to the determined location of the remaining drilling mud. The remaining drilling mud is removed using the focused ultrasound energy. Cement is deployed into the annular region having the remaining drilling mud removed therefrom.

A method for establishing a well for deep water drilling includes drilling a wellbore below the sea floor. A drilling mud is pumped into the wellbore. A casing is deployed into the wellbore. The drilling mud is removed from an annular region between the casing and the wellbore. Cement is deployed into the annular region. A location of a channel or other irregularity in the cement is determined. An ultrasound transducer is deployed down an interior of the casing. Ultrasound energy is focused, using the ultrasound transducer, to the determined location to mitigate the channel or other irregularity in the cement.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present disclosure and many of the attendant aspects thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram illustrating an application of high intensity focused ultrasound to the displacement of drilling mud in accordance with exemplary embodiments of the present invention;

FIG. 2 is a flow chart illustrating an approach for the application of high intensity focused ultrasound to the displacement of drilling mud in accordance with exemplary embodiments of the present invention;

FIG. 3 is a schematic diagram illustrating an ultrasound transducer array in accordance with exemplary embodiments of the present invention; and

FIG. 4 shows an example of a computer system capable of implementing the method and apparatus according to embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

In describing exemplary embodiments of the present disclosure illustrated in the drawings, specific terminology is employed for sake of clarity. However, the present disclosure is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents which operate in a similar manner.

Exemplary embodiments of the present invention seek to provide methods and apparatuses for more effectively clearing drilling mud and/or other obstructions from within a wellbore. Exemplary embodiments of the present invention also seek to provide methods and apparatuses for resolving obstructions in cement used in drilling. These goals may be accomplished, for example, by detecting precise locations of remaining mud deposits or other obstructions and then targeting high intensity focused ultrasound (HIFU) at the locations of the mud deposits or other obstructions to disrupt the obstructions. For example, where the obstruction is a quantity of hardened drilling mud, also known as mudcake, exemplary embodiments of the present invention may disrupt the mudcake and allow it to be cleared by subsequent and/or contemporaneous flush operations.

While exemplary embodiments of the present invention may be used to clear or otherwise correct for any type obstruction, an example of one obstruction that may be resolved in accordance with exemplary embodiments of the present invention is material that has collapsed off the surface of the wellbore and has fallen into the wellbore, for example, in the annular region between the wellbore and the casing. Thus not only can exemplary embodiments of the present invention be used to clear mudcake, but they may also be used to clear other obstruction that may present themselves.

Moreover, where an obstruction cannot be cleared away, exemplary embodiments of the present invention may be used to enlarge the size of the wellbore using the HIFU through a process of ultrasonic erosion. By enlarging the wellbore, the obstruction may be prevented from interfering with cement deployment. Additionally, or alternatively, the HIFU may be used to create a bypass channel within the wellbore to avoid the obstruction.

FIG. 1 is a schematic diagram illustrating an application of high intensity focused ultrasound to the displacement of drilling mud or resolving of other obstructions in accordance with exemplary embodiments of the present invention and FIG. 2 is a flow chart illustrating an approach for the application of high intensity focused ultrasound to the displacement of drilling mud or resolving of other obstructions in accordance with exemplary embodiments of the present invention. Exemplary embodiments of the present invention will now be described in detail with respect to FIGS. 1 and 2.

As discussed above, deep water drilling may be performed from a platform, rig, or ship 11 that is floated on the water's surface 12. First, a wellbore 14 may be drilled below the seafloor 13 (Step S201). The wellbore 14 may extend thousands of feet below the surface of the water 12. Drilling may be performed using one or more techniques known in the art. As the wellbore 14 is being drilled, or shortly thereafter, drilling mud may be pumped into the wellbore 14 (Step S202). The drilling mud so deployed may serve to preserve the integrity of the wellbore 14 as pressure and other environmental factors may otherwise act to collapse the wellbore 14.

A casing 15 may be lowered into the wellbore 14 (Step S203). The casing 15 may be deployed after drilling has been completed, however, the casing 15 may alternatively be deployed while drilling is being performed. The casing 15 may be substantially cylindrical with a hollow center like a pipe. An annular region may exist between the interior of the wellbore 14 and the exterior of the casing 15. Drilling mud may be at least partially cleared from this annular region (Step S204), for example, by performing a flushing operation. There may be no need to clear drilling mud from the interior of the casing as it may have been deployed in such a way as to avoid the drilling mud from entering the casing. The clearing of the drilling mud from the annular region may be performed either before the deployment of the casing, after the deployment of the casing or concurrently.

Thereafter, an ultrasound transducer array 17 may be lowered down the casing 15 from a wireline 16 (Step S205). FIG. 3 is a schematic diagram illustrating an ultrasound transducer array 17 in accordance with exemplary embodiments of the present invention. The ultrasound transducer array 17 may extend from the wireline 16 and may include a plurality of ultrasound transducers 20 arranged in a two-dimensional circular pattern on a mobile cylindrical platform in a shape that mirrors the curvature of the casing so that as the ultrasound transducer array 17 is lowered down the casing 15, it may be used to acquire images in 360°.

The ultrasound transducers 20 of the ultrasound transducer array 17 may alternatively be arranged as a two-dimensional matrix or array within a single surface or plane. For example, the ultrasound transducer array 17 may include a matrix of ultrasound transducers 20 mounted onto a single board, for example, in even rows and columns. According to one particular exemplary embodiment, the ultrasound transducers 20 may be arranged in a 4×4 grid.

Alternatively, rather than deploying an array of ultrasound transducers, a single ultrasound transducer may be used. However, for the purposes of providing a simple explanation, exemplary embodiments of the present invention may be described herein in terms of an ultrasound transducer array 17, even though only a single ultrasound transducer need be used.

The wireline 16 may provide a data bus for transmitting control signals down to the ultrasound transducer array 17 and for sending image data up to a control center located above the surface.

While FIG. 3 shows the ultrasound transducer array 17 including eight ultrasound transducers 20, any number of ultrasound transducers may be used. For example, the ultrasound transducer array 17 may include approximately ten ultrasound transducers, tens of ultrasound transducers or even hundreds of ultrasound transducers.

The ultrasound transducer array 17 may have approximately one third the diameter of the casing so that it may be effectively deployed without contacting the casing. Alternatively, the ultrasound transducer array 17 may be substantially similar in radius to the casing so that it may be guided down without unintended rotation. For example, the ultrasound transducers 20 may be built into the shape of a cylinder or disk so that the casing may prevent unintended rotation. The ultrasound transducer array 17 may also include retractable and/or spring-loaded feet that may contain wheels, ball bearings, or low-friction pads to more easily slide down the casing without unintended rotation. Alternatively, or additionally, the ultrasound transducer array 17 may engage one or more groves or tracks within the casing 15 for more effective deployment therein. However, another approach is to use a substantially rigid wireline 16 for precisely controlling the depth and angle of the ultrasound transducer array 17.

The ultrasound transducers 20 of the array 17 need not be arranged in a single ring. For example, the ultrasound transducers may be extended in a lengthwise direction, for example, with each transducer pointed in a different direction. Alternatively, the ultrasound transducers 20 may be arranged as a set of annular rings.

Alternatively, as described above, the ultrasound transducer array 17 may include only a single ultrasound transducer 20 and this ultrasound transducer 20 may be rotated as it is lowered, for example in a spiral motion, to acquire the ultrasound images in 360°. According to one approach, the ultrasound transducers 20 may rotate within the ultrasound transducer array 17 so that the ultrasound transducer array 17 need not rotate with respect to the casing 15.

Accordingly, as the ultrasound transducer array 17 is lowered down the casing 15, a sequence of ultrasound images may be acquired therefrom in 360°(Step S206). It is not necessary that imaging be performed using an ultrasound modality. Any mode of imaging may be used. However, for the purposes of providing a simple explanation, exemplary embodiments of the present invention may be described as using an ultrasound mode of imaging.

The ultrasound images may be analyzed in real-time or with some acceptable degree of delay as the ultrasound transducer array 17 is lowered down the casing 15 so that portions of drilling mud 18 within the annular region between the casing 15 and the wellbore 14 may be detected (Step S207). When drilling mud 18 is detected at a particular depth (Yes, Step S207), one or more of the ultrasound transducers 20 of the ultrasound transducer array 17 may be used to generate a high intensity focused ultrasound (HIFU) in the exact location of the detected drilling mud 18 (Step S208). The descent of the ultrasound transducer array 17 may be temporarily halted as this action is taken. Each ultrasound transducer 20 may generate a HIFU and each HIFU may be electronically and/or mechanically focused and directed to converge at the location of the detected drilling mud 18, for example, in the manner shown in FIG. 3 by the double-line arrows 30. Alternatively, only those ultrasound transducers 20 facing the detected drilling mud 18 may be used to generate the HIFU. Alternatively, only a single ultrasound transducer 20 that is most closely facing the detected drilling mud 18 may be used to generate the HIFU. Alternatively, where the ultrasound transducer array 17 only includes a single ultrasound transducer 20, the ultrasound transducer 20 may be rotated to face the detected drilling mud 18 prior to generating the HIFU.

The ultrasound transducer array 17, or each ultrasound transducer 20 thereof, may be set to provide HIFU with an acoustic power of about 100 W to about 2000 W that may be focused on a region with a diameter of about 5 millimeters to about 20 millimeters, with lower frequency systems having the ability to treat larger volumes. Alternatively, a greater acoustic power may be used, where available. It is to be understood that the higher the acoustic power being used, the less time the HIFU need be focused at a particular location, and the faster the process may be performed. Thus according to exemplary embodiments of the present invention, the maximum acoustic power used need only be limited by availability and practicality.

Each HIFU may be electronically and/or mechanically steered to cover a large area and range of depths. The detected drilling mud 18 may be disrupted by the application of the HIFU. Disruption of the drilling mud 18 or other obstruction may include any alteration to the properties of the obstruction that may serve to make the obstruction more easily movable, for example, so that a mudcake may be more easily cleared by subsequent means. For example, disruption may include directed pushing via ultrasound radiation force, liquefaction via pulsed insonication, and/or erosive cavitation. Exemplary embodiments may also combine one or more of these or other techniques in performing disruption. The ultrasound imaging, or other imaging modality used, may then be used to determine when the entire detected drilling mud 18 has been disrupted to a desired level. When the entire detected drilling mud or other obstruction has been disrupted, for example, broken down, detection may continue until the entire wellbore 14 has been cleared. When no obstruction is detected at a given depth (No, Step S207), the imaging may continue as the array 17 is further lowered.

HIFU may operate to breakdown or otherwise disrupt the hardened drilling mud deposits in a manner similar to how kidney stones may be destroyed in situ using ultrasonic waves. As HIFU is capable of delivering a significant amount of power to a targeted location sparing the regions surrounding the focal zone, this technique may be used to break down drilling mud deposits without harming the casing or the wellbore structure.

It is not necessary for the HIFU to completely disintegrate the drilling mud caked on the casing. Existing approaches for clearing drilling mud, such as flushing, may be performed and/or repeated. The HIFU may be successful in liquefying the mudcake to the point where it may be more easily cleared using existing techniques.

Where the obstruction is not a mudcake, but rather a channel or other imperfection within cement, for example, located in the annular region between the casing and the wellbore, HIFU may be used to disrupt the channel, for example, by performing liquefaction and causing the otherwise firm cement to flow more freely and thereby resolve the channeling.

Flushing (Step S209) may also be used in conjunction with HIFU to clear the mudcake from the annular region between the casing and the wellbore. According to this approach, HIFU may be used to loosen the mudcake either prior to flushing or as flushing is performed. Flushing may involve sending a pressurized liquid down the annular region to dissolve and displace the mudcake. Drilling mud that is not cleared by the flushing may be exposed to HIFU in the manner described above and then subsequent or continued flushing may operate to clear the lingering deposits, for example, as described in detail above.

Moreover, HIFU may be used during flushing to increase turbulence of the flushing liquid and assist the clearing. To accomplish this, a steady or pulsing current in the flushing fluid may be driven by the absorption of the high amplitude acoustic energy of the HIFU.

Exemplary embodiments of the present invention therefore seek to intentionally remotely breakdown of the mudcake and/or to enhance cement slurry uniformity and settling to mitigate voids in order improve final cement integrity. For this purpose, focused high intensity sound may be used to locally vibrate or locally push on the cement slurry, where the vibration or push is concentrated at the focus of the acoustic beam.

A principle behind these approaches is “acoustic streaming.” Essentially, during sound propagation, some portion of the acoustic power is absorbed by the media, whether it be the drilling mud or the cement. The change in momentum of the absorbed propagating phonons is converted to force acting on the absorbing media. This force, in turn, may cause flow in a fluid media. The magnitude of the flow may depend on the attenuation rate (absorption) of the media, the density of the media, the acoustic power level, and the viscosity of the fluid.

After all drilling mud has been cleared from the annular region between the casing and the wellbore, cement may be deposited within this region to support the casing and prevent communication between the interior and exterior of the well (Step S210). Techniques such as those described above may then be used to identify and resolve channels and/or other imperfections that may occur within this cement.

As described above, the same set of ultrasound transducers are used for imaging and delivering the HIFU. However, exemplary embodiments of the present invention need not be limited to this approach. Alternatively, conventional ultrasound imaging techniques may be used for mudcake detection and the above-described ultrasound transducer array may be used to breakdown the mudcake once detected. Thus according to this approach, different ultrasound devices may be responsible for imaging and delivering HIFU.

Moreover, the techniques described above for detecting regions of interest in the context of deep water drilling and delivering HIFU to these regions need not be limited to the detection and clearing of mudcake deposits. For example, exemplary embodiments of the present invention may be used to detect and remedy channels within the cement that is deployed between the casing and the wellbore to provide additional structural integrity to the cement.

The HIFU may constitute acoustic beams that are highly localized and may have the ability to impart localized vibrations to cause liquefaction of the cement in and around the vicinity of the channels in a phenomenon that is similar to soil liquefaction, in which seismic activity causes hard ground to obtain a nearly liquid consistency. Liquefaction may be performed to remediate detected channels even where the cement has partially or entirely become firm.

Control of the above-described method for performing high intensity focused ultrasound (HIFU) to the displacement of drilling mud in deep water drilling in accordance with exemplary embodiments of the present invention may be managed by a computer system running specially designed software. FIG. 4 shows an example of a computer system which may implement a method and system of the present disclosure.

The system and method of the present disclosure may be implemented in the form of a software application running on a computer system, for example, a mainframe, personal computer (PC), handheld computer, server, etc. The software application may be stored on a recording media locally accessible by the computer system and accessible via a hard wired or wireless connection to a network, for example, a local area network, or the Internet.

The computer system referred to generally as system 1000 may include, for example, a central processing unit (CPU) 1001, random access memory (RAM) 1004, a printer interface 1010, a display unit 1011, a local area network (LAN) data transmission controller 1005, a LAN interface 1006, a network controller 1003, an internal bus 1002, and one or more input devices 1009, for example, a keyboard, mouse etc. As shown, the system 1000 may be connected to a data storage device, for example, a hard disk, 1008 via a link 1007.

Exemplary embodiments described herein are illustrative, and many variations can be introduced without departing from the spirit of the disclosure or from the scope of the appended claims. For example, elements and/or features of different exemplary embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims. 

What is claimed is:
 1. A method for disrupting an obstruction from a wellbore, comprising: determining a location of an obstruction within a wellbore; deploying an ultrasound transducer down an interior of a casing in the wellbore; focusing ultrasound energy, using the ultrasound transducer, to the determined location of the obstruction; and disrupting the obstruction using the focused ultrasound energy.
 2. The method of claim 1, wherein determining the location of the obstruction within the wellbore includes: acquiring a sequence of ultrasound images, using the ultrasound transducer, of an area exterior to the casing, as the ultrasound transducer is deployed down the interior of the casing; analyzing the acquired images to detect the obstruction; and determining the location of the obstruction from the acquired images.
 3. The method of claim 2, wherein the acquired sequence of ultrasound images cover a 360° field.
 4. The method of claim 1, wherein the ultrasound transducer includes a plurality of ultrasound transducers.
 5. The method of claim 4, wherein the plurality of ultrasound transducers are arranged in a circle substantially conforming to a radius of the casing.
 6. The method of claim 4, wherein the plurality of ultrasound transducers are arranged along a lengthwise direction of the casing.
 7. The method of claim 4, wherein the plurality of ultrasound transducers are arranged in a two-dimensional pattern or grid that is substantially confined to a flat, curved, or irregular surface.
 8. The method of claim 7, wherein the two-dimensional pattern or grid is as wide as can be practically accommodated by the diameter of the casing.
 9. The method of claim 4, wherein the plurality of ultrasound transducers are arranged as a set of annular rings.
 10. The method of claim 1, wherein disrupting the obstruction includes breaking the obstruction down into a plurality of smaller sections or particles.
 11. The method of claim 1, wherein disrupting the obstruction includes increasing the movability of the obstruction.
 12. The method of claim 1, wherein disrupting the obstruction includes liquefying the obstruction via a pulsed insonication.
 13. The method of claim 1, wherein disrupting the obstruction includes performing erosive cavitation.
 14. The method of claim 1, wherein disrupting the obstruction includes enlarging the wellbore by ultrasonic erosion.
 15. The method of claim 1, wherein disrupting the obstruction includes creating or increasing a bypass channel around the obstruction.
 16. The method of claim 1, wherein prior to deploying the ultrasound transducer array down the interior of the casing, the wellbore is drilled, drilling mud is pumped therein, the casing is lowered into the wellbore, and an attempt to clear the drilling mud from an annular region between the exterior of the casing and interior of the wellbore is made.
 17. The method of claim 1, wherein the ultrasound transducer includes one or more ultrasound imaging devices for determining the location of the obstruction as the ultrasound transducer is deployed.
 18. The method of claim 1, wherein the obstruction includes drilling mud remaining in an annular region between the casing and the wellbore.
 19. The method of claim 1, wherein the obstruction includes a channel or other irregularity within cement in an annular region between the casing and the wellbore.
 20. The method of claim 1, wherein the obstruction includes material which has separated from the surface of the wellbore and has collapsed into the wellbore.
 21. The method of claim 1, wherein focusing the ultrasound energy includes performing high intensity focused ultrasound (HIFU).
 22. The method of claim 1, wherein disrupting the obstruction using the focused ultrasound energy includes performing a flushing operation to clear the obstruction after it has been at least partially broken down by the focused ultrasound energy.
 23. A method for establishing a well for deep water drilling, comprising: drilling a wellbore below the sea floor; pumping a drilling mud into the wellbore; deploying a casing into the wellbore; partially removing the drilling mud from an annular region between the casing and the wellbore; determining a location of an area of remaining drilling mud in the annular region; deploying an ultrasound transducer down an interior of the casing; focusing ultrasound energy, using the ultrasound transducer array, to the determined location of the remaining drilling mud; removing the remaining drilling mud using the focused ultrasound energy; and deploying cement into the annular region having the remaining drilling mud removed therefrom.
 24. A method for establishing a well for deep water drilling, comprising: drilling a wellbore below the sea floor; pumping a drilling mud into the wellbore; deploying a casing into the wellbore; removing the drilling mud from an annular region between the casing and the wellbore; deploying cement into the annular region; determining a location of a channel or other irregularity in the cement; deploying an ultrasound transducer down an interior of the casing; focusing ultrasound energy, using the ultrasound transducer, to the determined location to mitigate the channel or other irregularity in the cement. 